Gretchen Hildegard Mannkusser is a German woman who is the co-runner of The Grotto and the wife of Otto Mannkusser. She is the secondary boss of Francis and Piama, with Otto being the primary, starting with the episode Zoo.

Gretchen Mankusser is a kind and caring woman and it is not in her nature to be aggressive. She is the co-owner of a cattle ranch called "The Grotto" alongside her husband, Otto. The Grotto is named after both of them. "Gretchen" and "Otto" combined becomes "Grotto". Aside from her husband, Otto, Gretchen also has a teenage son named Rutger.

Much of Gretchen's backstory has been explored in the show. As Otto explained to Francis their marriage is deceit: Gretchen was actually the former fiance of Otto's childhood friend Manfred Schmidt, but Otto loved her as well. when they were planning to elope, Gretchen's intended arranged for her to meet him at a rendezvous point, but Otto lied about the actual location and told Manfred that they would meet at a train station in Berlin. When her fiance did not show up, she was left crying at the altar and Otto came and comforted her and eventually married and they had a son named Rutger Mannkusser who no longer lives with them and only made one appearance, when Manfred finally came to visit Gretchen to reconcile, Francis drove him off knowing the truth was better left unsaid to Gretchen.

When the Wilkerson's visited the ranch for the first time, in the episode Boys At Ranch, Dewey paid special attention to Gretchen's expensive doll collection and was trusted by Gretchen not to tamper with the dolls, Dewey did not live up to the promise and broke her favorite doll and Gretchen punished him by having him clean the house with her which they end up enjoying and she ends up forgiving Dewey.

Gretchen is an aspiring actress and has always wanted to be in movies and has some minor experience in acting. In episode Stereo Store, Francis allowed her to have her big break by hiring a studio to film at the ranch (though she was only picked for the role because the original actress dropped out). Francis eventually found out he accidentally hired a pornographic director and that the movie was going to be a porno. Francis desperately tried to evict the crew, despite knowing this would hurt Gretchen. After finding out that Gretchen didn't care what kind of movie she would be in (even if it was a porno), he allowed the set to stay and continue filming. The dialogue for the porno was left unedited, but the direction of what the characters did was changed to something non-sexual. Gretchen played a housekeeper at a hotel, who went into a man's room and gave him in food, dusted off all of his furniture, etc. She said things like "Put it there", but referred to putting a tray of food there, on a table and the entire scene carried out like that. Afterwards, Gretchen talked to Otto about the movie and said that the scene was kind of pointless and could have used more sex. Otto dismissed this, saying that Americans are very prudish and would not have allowed that.

In the episode Hal's Christmas Gift, Francis mentioned that he and Piama were finally fired from their jobs at The Grotto, because Francis deposited all of the ranch's money into what he thought was an ATM, but really wasn't. (What it really was is never mentioned) This means that this was the last that Gretchen would ever be heard of, leaving her last appearance in the show as the episode Hot Tub.